> The problem isn't so much the fuel, it's the ancient piston aircraft (or at least, ancient engine designs) that are still kicking around. Yes, that's my unde

> The problem isn't so much the fuel, it's the ancient piston aircraft (or at least, ancient engine designs) that are still kicking around. Yes, that's my understanding too. Aviation piston engines are stuck in 1950, largely because more stringent regulations have made it more expensive to develop new engines vs. keeping producing largely existing engine designs grandfathered in, and also because the market is pretty small. > There are modern piston aircraft engines that not only run fine on unleaded fuel [1], but are even certified to run on standard automotive fuel ("Mogas"). There are videos on YouTube of pilots landing on remote highways and pulling up to regular gas station pumps to refuel their aircraft! AFAIK the usefulness of this has been reduced, due to a lot of automotive gas containing ethanol. The engine itself might work fine with an ethanol blend, but the fuel system (bladders, lines, etc.) might not. There is apparently also a fear of vapor lock or other trouble if the ethanol and the rest of the fuel separate in the tank.